Commercial chemical sprayers for turf are well known. Such systems can be used for applying fertilizers and pesticides to a golf course, for example. The term "pesticide" will be used broadly herein to refer to any chemical, natural or man-made, which is intended to control or eliminate an unwanted plant, animal or insect, and would include but not be limited to herbicides, insecticides, fungicides and nematicides. While the present invention is not limited to commercial pesticide sprayers for turf, it will be described in that context for the sake of brevity.
FIG. 1 shows a schematic of a typical prior art turf sprayer. It includes a large tank for containing the chemical solution (made by mixing water and concentrated chemical). The chemical could be a pesticide, and this discussion will focus on same. Connected to the tank is a centrifugal pump, the outlet of which is connected to a pressure control valve, which in turn feeds a plurality of electric-solenoid operated on/off valves. Some of the liquid on the pressure side (i.e., the outlet) of the centrifugal pump is also returned to the tank to help mix the pesticide solution to keep it homogeneous. The outlet of each on/off valve is connected to a manifold carrying a plurality of spray nozzles which actually deliver the pesticide solution to the turf. There is also a return line running from the valves back to the main tank, so that when a valve is turned off, instead of the pressure increasing in the other lines, the solution is returned to the tank and the pressure at the other booms remains constant. Typically, the components of such a spray system are "off the shelf" and are plumbed together using standard hoses and fittings. One example of the spray system described above is the Multi Pro.RTM. dedicated spray vehicle sold by The Toro Company and manufactured by Hahn, Inc., the assignee of the present invention.
One advantage of the turf sprayer illustrated in FIG. 1 is that it has a relatively small number of off-the-shelf components and is relatively easy to construct and maintain. One disadvantage of the type of sprayer shown in FIG. 1 is that it doesn't automatically compensate for changes in the speed of the vehicle carrying the spray components. Thus, when the vehicle moves faster the system delivers relatively less pesticide solution per unit area. Another, and probably more significant problem, relates to the difficulty in properly disposing of the contents of the tank, after the spraying operation. The typical tank has a capacity of about 100 gallons, and if the operator ends the day with, say, 20 gallons of pesticide solution remaining, the operator has to store or dispose of a rather large volume of solution which is closely regulated by the U.S. Environmental Protection Agency (EPA). EPA regulations for most pesticides do not allow overnight storage of the pesticide solution in the spray tank, and proper disposal is extremely cumbersome. According to EPA regulations, leftover pesticide solution must be evenly dispensed over a previously untreated area or stored in the original concentrate container. It cannot simply be washed down the drain or dumped behind the maintenance shed. And the "leftover problem" arises not only at the end of the work day, but also when the operator wants to switch from one pesticide to another.
A more sophisticated spray system is schematically shown in FIG. 2. This type of system, also represented in the prior art, includes all of the components of the system shown in FIG. 1, but also includes means for compensating for varying vehicle speeds, so that the delivery rate of the solution per unit area remains more or less fixed. Specifically, the improved system shown in FIG. 2 includes a flow meter, pressure control valve and vehicle speed sensor connected to a controller. When the vehicle speeds up, the controller proportionally opens the pressure control valve to allow a larger flow of pesticide solution; and when the vehicle slows down, the controller proportionally closes the pressure control valve to allow a smaller flow of pesticide solution. The flow meter measures the flow to the boom and with this information the controller tells the control valve to open or close to achieve the target rate. Information at the controller is tabulated on gallons left in the tank and gallons applied to the turf via the flow meter.
While the more sophisticated system of FIG. 2 addresses one of the problems associated with the simplified system of FIG. 1 (i.e., the problem of a variable delivery rate per unit area depending on the vehicle speed), it does not address the problem of how to handle leftover pesticide solution. If the operator could predict precisely how much pesticide solution he or she would need for a given day or run, then that amount of pesticide solution could be mixed in the tank, and there would not be a "leftover problem". Of course, it is virtually impossible to accurately predict the exact volume of pesticide solution that will be needed in the course of a day or session.
Also, with regard to both systems (i.e., the systems shown in FIGS. 1 and 2), the EPA requires that the tank and other "contaminated" components be internally washed (triple rinsed or pressure washed) at the end of the day or before switching over to another chemical; and that the rinsate from this internal washing operation be stored in a properly marked container (not the sprayer tank) or spread over a fairly large and previously untreated area. Some states, for example Michigan, are even requiring golf courses to build rinsate capturing stations in or near their equipment maintenance sheds. A station of this type includes a large drain built into the floor and special tanks for storing pesticide rinsate for proper disposal of at a later time.
In addition to the "leftover" and "internal washing" problems discussed above. Applicant believes that it would be advantageous if operators would completely clean off the exteriors of their sprayers prior to returning to the maintenance shed. The spray booms, including the manifolds and nozzles, and the vehicles themselves often become coated with the chemical solution, and these components would preferably be cleaned in the field, rather than being rinsed off next to the maintenance shed.
Thus, prior art sprayers did not adequately address the three problems discussed above: the "leftover problem," the "internal washing problem" and the "external washing problem."